A method for systematically and automatically checking a product, whose preservation in a distribution network depends on the temperature, in particular a product subject to a cold chain, was described in the international patent application published under number WO 03/025529.
In the method described in this previous application, a marker is provided which changes the condition when the temperature of the product exceeds a certain temperature threshold, or when the preservation conditions deviate from a certain reference level, these conditions being either the exceeding of a certain temperature threshold for a period of time longer than a certain period of time or the exceeding of a certain preservation period of time.
In other words, the method described in this previous document provides for indications that depend on an exceeding of certain time or temperature thresholds or limits.
Heat-sensitive products, and in particular food products, are products which continuously depend on the link between time and temperature. The existence of a preservation temperature is only a recommendation making it possible to guarantee a period of time for using the product.
This is the case particularly for fresh food products.
In fact, standards, particularly those relating to food products, require a consume-by or use-by date, which depends on the temperature and preservation time conditions. For example, for a product that should be preserved at 0° C. to +4° C., the consume-by date determined by the authorities incorporates the exposure of the product, for a longer or shorter period of time, to a higher temperature (+8° C.) corresponding to a reasonable break in the cold chain (AFNOR standard NF V 01-003).
The present invention starts from the observation that the use-by dates are generally not optimal because they are determined based on presupposed preservation conditions. For example, for a perishable product that should be preserved at 0° C. to +4° C., its period of use may be extended compared to what the standard indicates if the product is not exposed to temperatures higher than +4° C., insofar as the said standard provides for an exposure to a temperature of +8° C. for a break in the cold chain. This means that some products are not consumed even though they might be, which constitutes a significant drawback both in practical and in economic terms.